The fabrication of ICs involves the formation of features on a substrate that make up circuit components, such as transistors, resistors and capacitors. The devices are interconnected, enabling the ICs to perform the desired functions. An important aspect of the manufacturing of ICs is the need to provide planar surfaces using planarization techniques.
To planarize substrates, chemical mechanical polishing (CMP) can be used. CMP tools generally include a platen with a polishing pad. A wafer carrier including a polishing head is provided. The polishing head holds the wafer so that the surface of the wafer to be polished faces the polishing pad. During polishing, the polishing head presses the wafer surface against a rotating polishing pad. Slurry which consists of small abrasive particles is provided between the wafer surface and the pad. The polishing head may also rotate and oscillate the wafer as it is being polished.
However, we have observed that non-uniformity can occur across the wafer with the use of conventional polishing heads. Such non-uniformity can lead to processing issues as well as negatively impacting yields.
From the foregoing discussion, it is therefore desirable to provide polishing heads with improved uniformity.